# Atomic layer deposition of ZnO/TiO2 nanolaminates as ultra-long life anode material for lithium-ion batteries

• 945 Accesses

• 1 Citations

## Abstract

In this work, we designed ZnO/TiO2 nanolaminates by atomic layer deposition (ALD) as anode material for lithium ion batteries. ZnO/TiO2 nanolaminates were fabricated on copper foil by depositing unit of 26 cycles ZnO/26 cycles TiO2 repeatedly using ALD. ZnO/TiO2 nanolaminates are much more stable than pristine ZnO films during electrochemical cycling process. Therefore, ZnO/TiO2 nanolaminates exhibit excellent lithium storage performance with an improved cycling performance and superior rate capability compared to pristine ZnO films. Moreover, coulombic efficiency (CE) of ZnO/TiO2 nanolaminates is above 99%, which is much higher than the value of pristine ZnO films. Excellent ultralong-life performance is gained for ZnO/TiO2 nanolaminates, retaining a reversible capacity of ~667 mAh g−1 within cut-off voltage of 0.05-2.5 V after 1200 cycles of charge-discharge at 500 mA g−1. Constructing nanolaminates structures via ALD might open up new opportunities for improving the performance of anode materials with large volume expansion in lithium ion batteries.

## Introduction

Rechargeable lithium ion batteries (LIBs) have attracted great attentions in energy storage area due to their high energy density and benign cycling life1,2,3,4. However, the current commercially used graphite anode with a relatively low theoretical capacity of 372 mAh g−1 cannot satisfy the increasing needs of the ever-enlarging market, especially in hybrid electric vehicles and electric vehicles. Therefore, transition metal oxides with higher theoretical capacities are intensively investigated as alternative anode to graphite5,6,7,8,9,10. Among them, zinc oxide (ZnO) exhibits promising properties, such as environmental benignity, high theoretical capacity (987 mAh g−1), as well as higher lithium ion diffusion coefficient compared to other transition metal oxides11,12,13. Nevertheless, ZnO electrodes usually suffer from poor electronic conductivity and huge volume change (228%) during lithiation and delithiation, resulting in poor electrochemical reaction kinetics and severe pulverization along with inferior cyclic stability and rate capability14,15. Therefore, rational design of high performance ZnO based anode for LIBs still remains a challenge. To this regard, great efforts have been devoted to improving the performance of ZnO anode, such as construction of various nanostructured electrodes and modification of ZnO16,17,18,19,20,21. For example, Xie et al. reported a ZnO based nanostructured anode of sandwich-like Ag-C@ZnO-C@Ag-C hybrid hollow microspheres, which exhibits a large reversible capacity of 1670 mAh g−1 after 200 cycles at a current density of 200 mA g−1 with excellent high-rate performance. The special structural features, including hollow structures, the sandwich-like shells, and the nanoscale dimension, contribute to the outstanding electrochemical performance22.

Atomic layer deposition (ALD) is a novel and promising thin film deposition technique based on sequential self-limited and complementary surface chemisorption reactions, which is able to deposit ultrathin, uniform, and conformal layers with precise thickness control23,24. This novel method has shown great prospects in preparation and modification of materials in energy area25,26, including anodes27,28, cathodes29,30, solid electrolytes31,32,33 of Li-ion batteries, as well as supercapacitors34. ALD has been used to improve the performance of ZnO anodes via depositing active ZnO onto carbon based supporters (graphene, carbon black, carbon foam, etc.)12,35 and surface modification36. For example, Zhao et al. reported that 3D carbon/ZnO nanomembrane foam prepared by ALD can retain 92% capacity after 700 cycles at 2 A g−1 and deliver a remarkable areal capacity of 4.3 mAh cm−235. Lu et al. fabricated ZnO-carbon black nanocomposites by directly depositing ZnO on carbon black using ALD, which exhibit excellent cyclic stability with a specific capacity of 1026 mAh g−1 maintained after 500 cycles12. Shi et al. utilized ALD Al2O3 coating to stabilize ZnO-graphene anode, which can maintained a reversible specific capacity of ~490 mAh g−1 after 100 cycles36.

Besides, ALD is a very powerful technique to construct novel nanostructures, various nanostructured electrodes have been designed and fabricated by ALD37. Nanolaminates are composite films consisted of alternating layers of different materials with individual layer thicknesses down to nanometer scale. ALD is ideally suited for fabricating nanolaminate films due to its precise thickness control of ~1 Å for the individual layers in the composites38. Herein, we designed the novel ZnO/TiO2 nanolaminates as anode materials for LIBs. ZnO/TiO2 nanolaminates were fabricated directly on copper foil by depositing 24 units of 26 cycles ZnO/26 cycles TiO2 repeatedly using ALD. Herein, ZnO is the main active material, providing high capacity. While, the inserted TiO2 layers are designed to stabilize ZnO from the following two considerations. Firstly, TiO2 can divide thick ZnO into multi-nanolayers, the dimension (thickness) of each ZnO layer is reduced to nanometer scale. Secondly, TiO2 is stable during charging-discharging process with the volume change of only 4%39,40. Therefore, the stable TiO2 thin films can also act as protective layers for ZnO. Accordingly, the electrochemical tests demonstrate that the reversible capacity and the rate performance of ZnO films are greatly improved after inserting TiO2 thin films. Moreover, ZnO/TiO2 nanolaminates exhibit excellent ultralong-life performance, retaining a reversible capacity of ~667 mAh g−1 almost without decay after 1200 cycles of charge-discharge at 500 mA g−1 with upper cut-off voltage of 2.5 V. Therefore, ZnO/TiO2 nanolaminates can work as ultra-long lifespan anodes in LIBs.

## Results

ZnO/TiO2 nanolaminates with ZnO/TiO2 thickness ratio of ~5:1 was designed. Considering the growth rate per cycle (GPC) is around 1.75 Å for ZnO and 0.36 Å for TiO2 in our system41,42, the nanolaminate was fabricated by depositing 24 alternate layers of ZnO (26 cycles) and TiO2 (26 cycles) with ZnO as the beginning layer. The schematic of ALD deposition process for ZnO/TiO2 nanolaminates is shown in Fig. S1. For comparison, the control sample of pristine ZnO film (624 cycles ZnO) was also prepared. Both samples were deposited directly onto Cu foil. The structure of samples are showed in Fig. 1.

SEM was performed to observe the surface morphology of pristine ZnO films and ZnO/TiO2 nanolaminates. In Fig. 2(a), it can be seen that pristine ZnO films deposited by ALD exhibit a lot of spindly grains with ~15 nm × 55 nm. After inserting TiO2 interlayer, ZnO/TiO2 nanolaminates show distinct morphology with much larger grain size of ~170 nm, as shown in Fig. 2(b). The grain size distribution is presented in Fig. S2 and S3. Due to the excellent conformality and uniformity of ALD, both films can cover the Cu foil conformally. EDS measurement in Fig. S4 provides the evidence for the presence of Zn, Ti, and O elements. In addition, the element mappings by EDS for the ZnO/TiO2 nanolaminates are also conducted, as shown in Fig. 2(c–e), which indicate that Zn, Ti and O elements are uniformly distributed over the whole surface. Moreover, the thickness is determined to be around 104 nm and 132 nm for pristine ZnO films and ZnO/TiO2 nanolaminates, respectively, from the cross-section FESEM images (Fig. S5). The crystallinity of as deposited ZnO and ZnO/TiO2 nanolaminates were also characterized by XRD, as shown in Fig. S6. It can be seen that as-deposited ZnO shows a weak (002) peak from hexagonal wurtzite ZnO. However, no peaks assigned to ZnO or TiO2 can be observed for ZnO/TiO2 nanolaminates. Inserting amorphous Al2O3 layer can inhibit the ZnO crystal growth has been reported by Elam et al.38. Therefore, amorphous TiO2 here can also reduce the crystallinity of ZnO.

The composition and chemical state of the ZnO/TiO2 nanolaminates were evaluated via XPS. The Zn 2p, Ti 2p and O 1 s signals centred at 1021.5, 458.7, and 529.9 eV can be easily found in the survey spectrum, revealing the coexistence of Zn, Ti and O in ZnO/TiO2 nanolaminates (Fig. 3a). In Fig. 3(b), Zn 2p exhibits two distinct peaks at 1044.5 eV and 1021.5 eV, which can be assigned to Zn 2p1/2 and Zn 2p3/2 peaks of Zn-O bonding with the spin orbit splitting energy of 23.0 eV, in good agreement with the value for ZnO43. In Fig. 3(c), the doublet with at 464.4 eV and 458.7 eV corresponds to Ti 2p1/2 and Ti 2p3/2 of Ti-O bonding with the spin orbit splitting energy of 5.7 eV, consistent with the value of TiO244. The spectrum of O 1 s (Fig. 3d) shows the main peak for O-Zn/O-Ti bonds of ZnO/TiO2 at 529.9 eV, the position of O-Zn and O-Ti are too close to be distinguished45,46. Besides, the peak related to -OH on the surface of ZnO/TiO2 nanolaminates at 531.6 eV can also be detected47. Both SEM EDS and XPS spectra can confirm that ZnO and TiO2 coexist in the films. In addition, the Zn/Ti atom distribution was also measured by XPS depth profile, as shown in Fig. S7, the multilayer structure of ZnO/TiO2 nanolaminates can be recognized. Cross-sectional TEM images also confirm the layer-by-layer structure of ZnO/TiO2 nanolaminates, as shown in Fig. S8.

Figure 4(a) shows the cyclic voltammograms (CV) of ZnO/TiO2 nanolaminates anode for the initial three cycles. Based on the previous literatures, the electrochemical process of ZnO towards lithium can be described as the following reactions48:

$${\rm{ZnO}}+2{{\rm{Li}}}^{+}+2{{\rm{e}}}^{-}\leftrightarrow {{\rm{Li}}}_{2}{\rm{O}}+{\rm{Zn}}$$
(1)
$${\rm{Zn}}+{{\rm{xLi}}}^{+}+{{\rm{xe}}}^{-}\leftrightarrow {{\rm{Li}}}_{{\rm{x}}}{\rm{Zn}}\,({\rm{x}}\le 1)$$
(2)

For ZnO/TiO2 nanolaminates, there are two small shoulders at ~0.59 V and 0.51 V as well as a broad peak centred at ~0.30 V can be discerned during the first cathodic scan. The shoulder at 0.59 V is derived from the decomposition of liquid electrolyte to form a solid electrolyte interphase (SEI) layer49,50. According to previous reports, the conversion reaction between ZnO and Li ion to generate Zn and Li2O generally takes place at ~0.50 V, while the subsequent alloying reaction between Zn and Li ion to produce LixZn alloys at around 0.25 V11. Two above-mentioned electrochemical reactions overlap partially here, therefore, a broad reduction peak centred at ~0.30 V and a small shoulder near 0.51 V can be observed. This phenomenon can be commonly observed in many other ZnO-based anodes22,36,51. In the subsequent first anodic scan, three peaks located between 0.20–0.80 V (0.36 V, 0.53 V and 0.79 V) are ascribed to the multistep dealloying process of LixZn alloy13. Another broad peak at 1.32 V can be related to the formation of ZnO by the redox reaction between Li2O and Zn52. In the subsequent two cycles, the CV curves show very good reproducibility, indicating high reversibility and excellent cycling stability of ZnO/TiO2 nanolaminates. The CV curves of pristine ZnO films shown in Fig. S9 are similar to those of ZnO/TiO2 nanolaminates. However, pristine ZnO films exhibit worse cycling stability than ZnO/TiO2 nanolaminates, as indicated with reduced enclosed CV area. In addition, pristine ZnO films exhibit an irreversible anodic peak at ~2.7 V, corresponding to the oxidation process of Zn back to ZnO. This peak disappears after 2 cycles, indicating the conversion reaction is irreversible for ZnO, same phenomenon has been observed in previous literature53.

Figure 4(b) plots the cycling performance of ZnO/TiO2 nanolaminates and pristine ZnO films at 500 mA g−1 for 100 cycles in the potential range of 0.05–2.0 V. It can be seen that the capacity of ZnO/TiO2 nanolaminates only drops in the initial few cycles, and then maintains a relatively stable capacity. Therefore, ZnO/TiO2 nanolaminates can maintain a reversible capacity of 381 mAh g−1 after 100 cycles at 500 mA g−1, demonstrating its excellent cycling performance. In contrast, pristine ZnO films exhibit a decreasing capacity along with cycling, only about 141 mAh g−1 can be remained after 100 cycles. Obviously, the cycling performance of ZnO/TiO2 nanolaminates is much better than pristine ZnO films. Fig. S10 exhibits the discharge/charge profiles ZnO and ZnO/TiO2 nanolaminates at 500 mA g−1 with cut-off potential of 0.05–2.0 V in 1st, 2rd, 3th, 50th and 100th cycle. More importantly, the CE of ZnO/TiO2 nanolaminates is above 99%, which is much higher than the value of pristine ZnO films. Especially in first 20 cycles, for example, the CE at 15th cycle is 99.0% and 96.2% for ZnO/TiO2 nanolaminates and pristine ZnO films, respectively. The cycling performance was also conducted at the current density of 200 mA g−1, as shown in Fig. S11 and S12, which shows the similar phenomena.

In order to explore the mechanism of enhanced electrochemical performance, SEM was performed to observe the morphology change after charging-discharging process. Figure 5(a) shows the SEM image of pristine ZnO films after 100 cycles cycling at the current density of 200 mA g−1. It can be seen that the spindly grains of ZnO are disappeared after cycling, leaving lots of small particles with the size less than 10 nm. It implies that the pulverization is very severe for pristine ZnO film during cycling. It has been demonstrated in previous reports that ZnO materials possess large volume expansion (228%) upon cycling, which would lead to severe pulverization for ZnO11,13. In contrast, the morphology of ZnO/TiO2 nanolaminates is much more stable than pristine ZnO, as shown in Fig. 5(b). Although the pulverization of grains still can be observed after cycling, large grain of ZnO/TiO2 nanolaminates is almost retained, suggesting its superior structural stability. Even cycled at high current density of 500 mA g−1 for 100 cycles, ZnO/TiO2 nanolaminates can still maintain its structure, as shown in Fig. S13. In addition, EDS was also conducted for ZnO/TiO2 nanolaminates after 100 cycling of 500 mA g−1, as shown in Fig. S14. It can be seen that Zn, Ti, O elements are still uniformly distributed after cycling. It can be demonstrated that ZnO/TiO2 nanolaminates are much more stable than pristine ZnO films.

Furthermore, we also explore the effect of cut-off voltage on the performance of ZnO/TiO2 nanolaminates. Therefore, cycling performance was also conducted in the potential range of 0.05–2.5 V for comparison, as shown in Fig. S15. It can be easily seen that larger cycling potential range delivers higher capacity. Moreover, ZnO/TiO2 nanolaminates can still show great cycling stability, exhibiting a reversible capacity of 875 and 706 mAh g−1 after 100 cycles at 200 and 500 mA g−1, respectively. Therefore, long-life cycling and rate capability were also performed in the potential range of 0.05–2.5 V. Figure 6(a) plots the long-life cycling performance conducted at 500 mA g−1 for 1200 cycles within the voltage of 0.05–2.5 V. The capacity only decreases at the initial several cycles. After that, the reversible capacity can be stabilized at ~667 mAh g−1 almost without decay, revealing a remarkable long-life performance. The rate capability of ZnO/TiO2 nanolaminates was also evaluated, as shown in Fig. 6(b), which was performed from 200 mA g−1 to 3200 mA g−1. It can be clearly seen that the ZnO/TiO2 nanolaminates exhibit excellent capacity retention at various current densities. Even at a high current density of 3200 mA g−1, a high capacity of ~307 mAh g−1 can be achieved, demonstrating a superior high-rate performance of ZnO/TiO2 nanolaminates. Furthermore, the cell is able to deliver a reversible capacity of 750 mAh g−1 when the current density returns back to 200 mA g−1. While pristine ZnO films show very poor rate ability.

To explore the charge transfer and Li ion diffusion characteristics in the pristine ZnO films and ZnO/TiO2 nanolaminates, EIS measurements were further conducted. Figure 7(a) compares the Nyquist plots of ZnO films and ZnO/TiO2 nanolaminates. Obviously, both Nyquist plots exhibit a semicircle in the high-middle frequency region and a slop line in the low frequency region. According to the reported literatures, the semicircle in high-frequency region is ascribed to the formation of the SEI layer and contacting impedance between active materials and electrolyte, the semicircle in the middle frequency range is assigned to the charge-transfer resistance (Rct) of electrode/electrolyte interface. The slopping line in low frequency region corresponds to diffusion of Li ion in electrodes54. Therefore, the EIS data were fitted using the mode of the insert in Fig. 7(a)55. Herein, Rs, RSEI, and Rct represent electrolyte resistance, SEI resistance, and charge-transfer resistance, respectively. CPE is the respective constant-phase element contributing to the semicircle in the experimental spectra. And W is the Warburg impedance. The fitted data are listed in Table 1. The SEI resistance and the charge-transfer resistance of the ZnO/TiO2 nanolaminates are lower than pristine ZnO films. Furthermore, Randles plots (Warburg impedance (Zw) vs. ω−1/2) of both electrodes were built, as shown in Fig. 7(b), where the slope of the fitted line in low frequency region is the Warburg coefficient (σw)56. The diffusion coefficient of Li ion (DLi + ) is inversely proportional to σw257,58. Obviously, the value of σw for ZnO/TiO2 nanolaminates electrodes is smaller than that of ZnO films electrodes, thereby possessing higher DLi+. It is observed that the Warburg coefficients (σw) of ZnO films and ZnO/TiO2 nanolaminates electrodes are 1394.0 and 642.6, respectively. The EIS measurements indicate that the formation of ZnO/TiO2 nanolaminates can decrease the SEI resistance and charge-transfer resistance, as well as improve the solid state Li ion diffusion in ZnO electrode. Accordingly, the superior lithium storage characteristics are exhibited in ZnO/TiO2 nanolaminates electrode compared to pristine ZnO films.

The excellent electrochemical performance of ZnO/TiO2 nanolaminates as anodes of LIBs can be ascribed to the following factors. (1) The dimension (thickness) of each active ZnO layer is reduced to nanometer scale. (2) Moreover, each active ZnO layers are protected by stable thin TiO2 layers from both side. Both above two factors can contribute to improving the stability of ZnO, therefore a remarkable electrochemical performance can be achieved.

## Conclusions

In summary, a novel nanostructured anode of ZnO/TiO2 nanolaminates was developed in this work, which was constructed by depositing unit of 26 cycles ZnO/26 cycles TiO2 repeatedly using ALD. It is demonstrated that ZnO/TiO2 nanolaminates are much stable than pristine ZnO films during electrochemical cycling process. Accordingly, the electrochemical tests demonstrate that the reversible capacity and the rate performance of ZnO films are greatly improved after inserting TiO2 thin films. Moreover, ZnO/TiO2 nanolaminates exhibit excellent ultralong-life performance, retaining a reversible capacity of ~667 mAh g−1 in potential range of 0.05–2.5 V almost without decay after 1200 cycles of charge-discharge at 500 mA g−1. In addition, EIS measurements indicate that the formation of ZnO/TiO2 nanolaminates can decrease the SEI resistance and charge-transfer resistance, as well as improve the solid state Li ion diffusion in bulk electrode. Above results imply that constructing nanolaminates structures via ALD might open up new opportunities for improving the performance of anode materials with large volume change in LIBs. ALD exhibits excellent large area uniformity, conformality, and precise thickness control. Therefore, it is very suitable for large scale fabrication. However, the cost of ALD may be too expensive to be used in LiBs for active materials deposition at present. Nowadays, various new type of ALD are researched to solve the cost problem, such as spatial ALD. We believe that ALD will play an important role in energy area in soon future.

## Methods

### Fabrication of ZnO/TiO2 nanolaminates

In ALD process, diethyl zinc (DEZ, 6N, Nata Opto-electronic Material Co., Ltd), titanium tetrachloride (TiCl4, 5N, Suzhou Fornano Corporation Ltd.) and deionized water were used as Zn, Ti precursors and oxygen source, respectively. All the precursors were kept at room temperature. Pure N2 (5N) was used as carrier and purge gas. ALD process was performed at 130 °C in a commercial Picosun SUNALETM R-200 ALD reactor. ZnO/TiO2 nanolaminates were fabricated through an alternate deposition of ZnO and TiO2 by ALD. Pulse time of three precursors was 0.1 s with a 4 s N2 purging step to remove the redundant reactants and by-products. In our ALD systems, the growth rate per cycle (GPC) is around 1.75 Å for ZnO and 0.36 Å for TiO241,42. Herein, we designed the ZnO/TiO2 nanolaminates with ZnO/TiO2 thickness ratio of around 5:1. Therefore, the nanolaminate was fabricated by depositing 24 alternate layers of ZnO (26 cycles) and TiO2 (26 cycles) with ZnO as the beginning layer. For comparison, the control sample of pristine ZnO film (624 cycles ZnO) was also prepared. Both samples were deposited directly onto Cu foil.

### Materials characterizations

The surface chemical features were investigated by X-ray photoelectron spectroscopy (XPS, Thermo Fisher K-Alpha) with standard Al Kα (1486.7 eV) X-ray source. The binding energies were calibrated using the signal from the adventitious carbon (binding energy C 1 s = 284.6 eV).

XPS spectra were fitted using Gaussian–Lorentzian functions. XPS depth profile was obtained by performing the XPS elemental scan after each 30 s Ar ion of 1000 eV etching. The resolution and sensitivity of XPS instrument is 0.35 eV and 3.7 kcps, which is measured by the full width at half maximum (FWHW). The microstructure and morphology were examined by field emission scanning electron microscopy (FESEM, Ultra 55, ZEISS) in InLens mode with voltage of 3 kV. Energy-dispersive X-ray spectroscopy (EDS) were performed to explore the element distribution in the same SEM system with the voltage of 18 kV. Crystallinity of thin films on Cu foil was analysed by a Rigaku-D/MAX 2000x-ray diffraction (XRD) system with Cu Kα radiation. Transmission electron microscopy (TEM, Tecnai F20 S-Twin, FEI) was conducted to observe the layer-by-layer structure of nanolamintes. The sample for TEM cross-section characterization was prepared by the combination of mechanical grinding and ion beam thinning.

### Electrochemical measurements

2032-type coin half-cells were used for the electrochemical measurements. The pristine ZnO films or ZnO/TiO2 nanolaminates on copper foil were directly used as the working electrodes. A metallic lithium foil served as both the counter electrode and the reference electrode. The porous polypropylene film (Celgard 2500) was used as the separator. A solution of 1 M LiPF6 dissolved in a mixture of ethylene carbonate (EC) and dimethyl carbonate (DEC) (1:1, w/w) was used as liquid electrolyte. The coin cells were assembled in an argon-filled glove box, in which oxygen and water contents were less than 1 ppm. The galvanostatic charge-discharge tests were performed using a battery testing system (LAND CT2001A) at various current densities in the potential range between 0.05 V–2.0 V and 0.05 V−2.5 V. Cyclic voltammetry evaluations (CV) were conducted at the scanning rate of 0.3 mV/s at a voltage between 0 V–3 V using an electrochemical workstation (CHI 660E). Electrochemical impedance spectroscopy (EIS) were taken on the same electrochemical workstation by applying an AC voltage amplitude of 5 mV in the frequency range of 10 mHz ~100 kHz on the open circuit voltage of the cells.

## References

1. 1.

Poizot, P., Laruelle, S., Grugeon, S., Dupont, L. & Tarascon, J. M. Nano-sized transition-metal oxides as negative-electrode materials for lithium-ion batteries. Nature 407, 496 (2000).

2. 2.

Nam, K. T. et al. Virus-Enabled Synthesis and Assembly of Nanowires for Lithium Ion Battery Electrodes. Science 312, 885 (2006).

3. 3.

Scrosati, B., Hassoun, J. & Sun, Y.-K. Lithium-ion batteries. A look into the future. Energy & Environmental Science 4, 3287–3295 (2011).

4. 4.

Li, M., Lu, J., Chen, Z. & Amine, K. 30 Years of Lithium-Ion Batteries. Advanced Materials 18, 3941–3946 (2018).

5. 5.

Zhang, W.-M., Wu, X.-L., Hu, J.-S., Guo, Y.-G. & Wan, L.-J. Carbon Coated Fe3O4 Nanospindles as a Superior Anode Material for Lithium-Ion Batteries. Advanced Functional Materials 18, 3941–3946 (2008).

6. 6.

Lin, J. et al. Graphene Nanoribbon and Nanostructured SnO2 Composite Anodes for Lithium Ion Batteries. ACS Nano 7, 6001–6006 (2013).

7. 7.

Zhao, Y. et al. Recent Developments and Understanding of Novel Mixed Transition-Metal Oxides as Anodes in Lithium Ion Batteries. Advanced Energy Materials 6, 1502175 (2016).

8. 8.

Yue, G. H. et al. Flower-like Nickel Oxide Nanocomposites Anode Materials for Excellent Performance Lithium-ion Batteries. Electrochimica Acta 152, 315–322 (2015).

9. 9.

Zhang, X. X., Xie, Q. S., Yue, G. H. & Zhang, Y. A novel hierarchical network-like Co3O4 anode material for lithium batteries. Electrochimica Acta 111, 746–754 (2013).

10. 10.

Xie, Q. et al. Facile fabrication of various zinc-nickel citrate microspheres and their transformation to ZnO-NiO hybrid microspheres with excellent lithium storage properties. Scientific Reports 5, 8351 (2015).

11. 11.

Zhang, G. et al. High-performance and ultra-stable lithium-ion batteries based on MOF-derived ZnO@ZnO quantum dots/C core-shell nanorod arrays on a carbon cloth anode. Advanced Materials 27, 2400–2405 (2015).

12. 12.

Lu, S., Wang, H., Zhou, J., Wu, X. & Qin, W. Atomic layer deposition of ZnO on carbon black as nanostructured anode materials for high-performance lithium-ion batteries. Nanoscale 9, 1184–1192 (2017).

13. 13.

Xu, G. L. et al. PEDOT-PSS coated ZnO/C hierarchical porous nanorods as ultralong-life anode material for lithium ion batteries. Nano Energy 18, 253–264 (2015).

14. 14.

Kushima, A. et al. Leapfrog Cracking and Nanoamorphization of ZnO Nanowires during In Situ Electrochemical Lithiation. Nano Letters 11, 4535 (2011).

15. 15.

Zhang, Y., Wang, Z., Li, Y. & Zhao, K. Lithiation of ZnO nanowires studied by in-situ transmission electron microscopy and theoretical analysis. Mechanics of Materials 91, 313–322 (2015).

16. 16.

Kundu, S. et al. Structural interpretation of chemically synthesized ZnO nanorod and its application in lithium ion battery. Applied Surface Science 329, 206–211 (2015).

17. 17.

Kim, J., Hong, S.-A. & Yoo, J. Continuous synthesis of hierarchical porous ZnO microspheres in supercritical methanol and their enhanced electrochemical performance in lithium ion batteries. Chemical Engineering Journal 266, 179–188 (2015).

18. 18.

Li, J. et al. Metal-organic frameworks derived yolk-shell ZnO/NiO microspheres as high-performance anode materials for lithium-ion batteries. Chemical Engineering Journal 335, 579–589 (2018).

19. 19.

Shen, X., Mu, D., Chen, S., Wu, B. & Wu, F. Enhanced electrochemical performance of ZnO-loaded/porous carbon composite as anode materials for lithium ion batteries. Acs Appl Mater Interfaces 5, 3118–3125 (2013).

20. 20.

Köse, H., Karaal, Ş., Aydın, A. O. & Akbulut, H. A facile synthesis of zinc oxide/multiwalled carbon nanotube nanocomposite lithium ion battery anodes by sol–gel method. Journal of Power Sources 295, 235–245 (2015).

21. 21.

Xie, Q. et al. Yolk-shell ZnO-C microspheres with enhanced electrochemical performance as anode material for lithium ion batteries. Electrochimica Acta 125, 659–665 (2014).

22. 22.

Xie, Q. et al. Electrostatic Assembly of Sandwich-Like Ag-C@ZnO-C@Ag-C Hybrid Hollow Microspheres with Excellent High-Rate Lithium Storage Properties. Acs Nano 10, 1283 (2015).

23. 23.

George, S. M. Atomic Layer Deposition: An Overview. Chemical Reviews 110, 111–131 (2010).

24. 24.

Johnson, R. W., Hultqvist, A. & Bent, S. F. A brief review of atomic layer deposition: from fundamentals to applications. Materials today 17, 236–246 (2014).

25. 25.

Guan, C. & Wang, J. Recent Development of Advanced Electrode Materials by Atomic Layer Deposition for Electrochemical Energy Storage. Advanced Science 3, 1500405 (2016).

26. 26.

Meng, X., Yang, X.-Q. & Sun, X. Emerging Applications of Atomic Layer Deposition for Lithium-Ion Battery Studies. Advanced Materials 24, 3589–3615 (2012).

27. 27.

Meng, X., Cao, Y., Libera, J. A. & Elam, J. W. Atomic Layer Deposition of Aluminum Sulfide: Growth Mechanism and Electrochemical Evaluation in Lithium-Ion Batteries. Chemistry of Materials 29, 9043–9052 (2017).

28. 28.

Li, X. et al. Batteries: Tin Oxide with Controlled Morphology and Crystallinity by Atomic Layer Deposition onto Graphene Nanosheets for Enhanced Lithium Storage. Advanced Functional Materials 22, 1646–1646 (2012).

29. 29.

Meng, X. et al. High-Performance High-Loading Lithium-Sulfur Batteries by Low Temperature Atomic Layer Deposition of Aluminum Oxide on Nanophase S Cathodes. Advanced Materials Interfaces 4, 1700096 (2017).

30. 30.

Kong, J.-Z. et al. Ultrathin ZnO coating for improved electrochemical performance of LiNi0.5Co0.2Mn0.3O2 cathode material. Journal of Power Sources 266, 433–439 (2014).

31. 31.

Cao, Y., Meng, X. & Elam, J. W. Atomic Layer Deposition of LixAlyS Solid-State Electrolytes for Stabilizing Lithium-Metal Anodes. ChemElectroChem 3, 858–863 (2016).

32. 32.

Liu, J. et al. Atomic Layer Deposition of Lithium Tantalate Solid-State Electrolytes. The Journal of Physical Chemistry C 117, 20260–20267 (2013).

33. 33.

Kozen, A. C., Pearse, A. J., Lin, C.-F., Noked, M. & Rubloff, G. W. Atomic Layer Deposition of the Solid Electrolyte LiPON. Chemistry of Materials 27, 5324–5331 (2015).

34. 34.

Cao, Y.-Q. et al. ZnO/ZnS Core-Shell Nanowires Arrays on Ni Foam Prepared by Atomic Layer Deposition for High Performance Supercapacitors. Journal of The Electrochemical Society 164, A3493–A3498 (2017).

35. 35.

Zhao, Y. et al. Three dimensional carbon/ZnO nanomembranes foam as lithium-ion anode with long-life and high areal capacity. Journal of Materials Chemistry A 6, 7227–7235 (2018).

36. 36.

Yu, M., Wang, A., Wang, Y., Li, C. & Shi, G. An alumina stabilized ZnO-graphene anode for lithium ion batteries via atomic layer deposition. Nanoscale 6, 11419–11424 (2014).

37. 37.

Knez, M., Nielsch, K. & Niinistö, L. Synthesis and surface engineering of complex nanostructures by atomic layer deposition. Advanced Materials 19, 3425–3438 (2007).

38. 38.

Elam, J., Sechrist, Z. & George, S. ZnO/Al2O3 nanolaminates fabricated by atomic layer deposition: growth and surface roughness measurements. Thin Solid Films 414, 43–55 (2002).

39. 39.

Chen, Z., Belharouak, I., Sun, Y. K. & Amine, K. Titanium-Based Anode Materials for Safe Lithium-Ion Batteries. Advanced Functional Materials 23, 959–969 (2013).

40. 40.

Zhang, Y., Tang, Y., Li, W. & Chen, X. Nanostructured TiO2-based Anode Materials for High-performance Rechargeable Lithium-ion Batteries. Chemnanomat 2, 764–775 (2016).

41. 41.

Cao, Y. Q. et al. Photocatalytic activity and photocorrosion of atomic layer deposited ZnO ultrathin films for the degradation of methylene blue. Nanotechnology 26, 024002 (2015).

42. 42.

Qin, C. C. et al. Improvement of electrochemical performance of nickel rich LiNi0.6Co0.2Mn0.2O2 cathode active material by ultrathin TiO2 coating. Dalton Transactions 45, 9669–9675 (2016).

43. 43.

Nefedov, V. I., Salyn, Y. V., Leonhardt, G. & Scheibe, R. A comparison of different spectrometers and charge corrections used in X-ray photoelectron spectroscopy. Journal of Electron Spectroscopy & Related Phenomena 10, 121–124 (1977).

44. 44.

Guo, X. et al. Porous TiB2-TiC/TiO2 heterostructures: Synthesis and enhanced photocatalytic properties from nanosheets to sweetened rolls. Applied Catalysis B: Environmental 217, 12–20 (2017).

45. 45.

Strohmeier, B. R. & Hercules, D. M. Surface spectroscopic characterization of the interaction between zinc ions and γ-alumina. Journal of Catalysis 86, 266–279 (1984).

46. 46.

Wagner, C. D., Zatko, D. A. & Raymond, R. H. Use of the oxygen KLL Auger lines in identification of surface chemical states by electron spectroscopy for chemical analysis. Analytical Chemistry 52, 1445–1451 (1980).

47. 47.

Yan, X. et al. The interplay of sulfur doping and surface hydroxyl in band gap engineering: Mesoporous sulfur-doped TiO2 coupled with magnetite as a recyclable, efficient, visible light active photocatalyst for water purification. Applied Catalysis B: Environmental 218, 20–31 (2017).

48. 48.

Fu, Z. W., Huang, F., Zhang, Y., Chu, Y. & Qin, Q. Z. The Electrochemical Reaction of Zinc Oxide Thin Films with Lithium. Journal of the Electrochemical Society 150, A714–A720 (2003).

49. 49.

Li, N., Jin, S. X., Liao, Q. Y. & Wang, C. X. ZnO anchored on vertically aligned graphene: binder-free anode materials for lithium-ion batteries. ACS Applied Materials & Interfaces 6, 20590–20596 (2014).

50. 50.

Wu, M.-S. & Chang, H.-W. Self-Assembly of NiO-Coated ZnO Nanorod Electrodes with Core–Shell Nanostructures as Anode Materials for Rechargeable Lithium-Ion Batteries. The Journal of Physical Chemistry C 117, 2590–2599 (2013).

51. 51.

Wang, Y., Jiang, X., Yang, L., Jia, N. & Ding, Y. In situ synthesis of C/Cu/ZnO porous hybrids as anode materials for lithium ion batteries. ACS Applied Materials & Interfaces 6, 1525–1532 (2014).

52. 52.

Qiao, L. et al. Single electrospun porous NiO-ZnO hybrid nanofibers as anode materials for advanced lithium-ion batteries. Nanoscale 5, 3037–3042 (2013).

53. 53.

Liu, Z. et al. Dramatically Enhanced Li-Ion Storage of ZnO@C Anodes through TiO2 Homogeneous Hybridization. Chemistry-A European Journal 25, 582–589 (2019).

54. 54.

Huang, G., Xu, S., Lu, S., Li, L. & Sun, H. Porous polyhedral and fusiform Co3O4 anode materials for high-performance lithium-ion batteries. Electrochimica Acta 135, 420–427 (2014).

55. 55.

Tan, H., Cho, H. W. & Wu, J. J. Binder-free ZnO@ZnSnO3 quantum dots core-shell nanorod array anodes for lithium-ion batteries. Journal of Power Sources 388, 11–18 (2018).

56. 56.

Wang, B. et al. An efficient route to a hierarchical CoFe2O4@graphene hybrid films with superior cycling stability and rate capability for lithium storage. Electrochimica Acta 146, 679–687 (2014).

57. 57.

Hsieh, C. T., Mo, C. Y., Chen, Y. F. & Chung, Y. J. Chemical-wet Synthesis and Electrochemistry of LiNi1/3Co1/3Mn1/3O2 Cathode Materials for Li-ion Batteries. Electrochimica Acta 106, 525–533 (2013).

58. 58.

Wu, X., Li, S., Wang, B., Liu, J. & Yu, M. One-step synthesis of the nickel foam supported network-like ZnO nanoarchitectures assembled with ultrathin mesoporous nanosheets with improved lithium storage performance. RSC Advances 5, 81341–81347 (2015).

## Acknowledgements

This work is supported in part by the Natural Science Foundation of China (51802150, 51721001, 51571111) and Jiangsu Province (BK20161397, and BK20170645), and a grant the State Key Program for Basic Research of China (2015CB921203), China Postdoctoral Science Foundation (2017M611778) and the Fundamental Research Funds for the Central Universities (021314380117). Dr. Aidong Li also thanks the support from the open project of NLSSM (M30038).

## Author information

Y.Q.C. and S.S.W. carried out the sample fabrication and electrochemical measurements. C.L. conducted XPS test. A.D.L. and D.W. participated in the discussion of results. Y.Q.C. drafted the manuscript. A.D.L. supervised the whole work and revised the manuscript. All authors critically read and commented on the manuscript.

Correspondence to Ai-Dong Li.

## Ethics declarations

### Competing Interests

The authors declare no competing interests.

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

## Rights and permissions

Reprints and Permissions

Cao, Y., Wang, S., Liu, C. et al. Atomic layer deposition of ZnO/TiO2 nanolaminates as ultra-long life anode material for lithium-ion batteries. Sci Rep 9, 11526 (2019) doi:10.1038/s41598-019-48088-2

• ### Conducting polymers and composites nanowires for energy devices: A brief review

• Larissa Bach-Toledo
• , Bruna M. Hryniewicz
• , Luís F. Marchesi
• , Luiz H. Dall'Antonia
• , Marcio Vidotti
•  & Franciele Wolfart

Materials Science for Energy Technologies (2020)